Ear pads



July 4, 1961 R. E. ULRICH ETAL 2,9 0,553

EAR PADS Filed July 20, 1959 INVENTORS RUBERI E. ULRICH Emma AlannaUnited States Patent 2,990,553 EAR PADS Robert E. Ulrich, Riverton, andGeorge A. Taylor, Gloucester, N.J., assignors to Radio Corporation ofAmerica, a corporation of Delaware Filed July 20, 1959, Ser. No. 828,3109 Claims. (Cl. 2-209) This invention relates generally to devices forprotecting the ears of a person from noise, and more particularly toimproved, noise attenuating ear pads adapted to be disposed between therigid ear cups of a noise protective device and the head of a person.The ear pads of the present invention are especially useful forpersonnel located in the vicinity of loud, ambient noises.

Discomfort and even loss of hearing have been induced in people byambient noise levels approching 100 decibels and higher. Thus, thepossibility of damaging their hearing presents a serious problem to allpersonnel who must work near high level noise operations. It has beenproposed to attenuate ambient noises by providing personnel with earcups having ear pads of soft rubber or of a plastic sheath containing aliquid. While these prior art devices have been useful in attenuatingambient noises appreciably and in relieving discomfort, they have notbeen altogether satisfactory. Moreover, it is desired to attenuateambient noise still further than the attenuation afforded by the priorart pads.

In cases where liquid-filled ear pads of a plasticized material areused, it is found that the hair and body oils of a user removes theplasticizer from the plastic, liquid containing sheath. The plastic padsthen readily deteriorate, so that their usefulness is relatively shortlived. In many cases, especially where water has been used as part ofthe liquid filler within the ear pads, it is found that the liquideventually evaporates through the plastic sheath walls.

Accordingly, it is an object of the present invention to provideimproved ear pads for use with noise protective devices to efficientlyattenuate ambient noise, and also which are relatively free from theaforementioned and other disadvantages of previously known pads.

It is a further object of the present invention to provide improved earpads that have superior noise attenuating properties over ear pads ofthe prior art, and that resist deterioration with prolonged use.

Still a further object of the present invention is to provide improvedear pads having a filler that will remain operable to attenuate noiseover a relatively wide range of temperatures.

It is another object of the present invention to provide improved,detachable, noise attenuating, ear pads that are relatively simple instructure, are easy to manufacture, and are highly efiicient in use.

In accordance with the present invention, the improved ear pads comprisetube-like sheaths of a plasticized plastic, each sheath preferably beingpartially collapsed and completely filled with a mixture of paste-likeconsistency. This mixture comprises a suspension of an inert powdersuspended in a suitable medium, and which may comprise a colloidalsuspension. The mixture may also contain, in addition to the suspendingmedium and the inert powder, a plasticizer for the plastic sheath. Theplasticizer in the mixture serves to replace any plasticizer that may beremoved from the plastic sheath by the hair and body oils of a personwearing the ear protective device. Deterioration of the ear pads is thusgreatly retarded. Ear pads filled with the paste-like mixtures of thepresent invention have excellent noise attenuating properties, remainoperable over a wide range of temperatures, and are more durable thanprior art pads.

The novel features of the present invention, both as Patented July 4.,1961 to its organization and method of operation, as well as additionalobjects and advantages thereof, will be understood more readily from thefollowing description, when read in connection with the accompanyingdrawings in which similar reference characters designate similar parts,and in which:

. FIG. 1 is a perspective view of an ear protective device employingimproved ear pads according to the present invention; and

FIG. 2 is a cross-sectional view taken along the line 2-2 in FIG. I,viewed in the direction indicated by the arrows, and showing theinternal structure of one of the ear pads of FIG. 1.

Referring, now, to FIG. 1, there is shown a noise protective device 10having a pair of similar, rigid, circumaural ear cups 12 and 14 ofplastic or other suitable material. Each of the ear cups 12 and 14 ismounted on a separate one of the two respective ends of a headband 16.The headband 16 comprises two generally parallelly disposed, resilientwires 18 and 20 held in substantially parallel alignment by a strip 22of flexible material, such as rubber or a plastic.

The ear cups 12 and 14 are both formed, on the front portions thereof,with two, laterally extending apertured ears 24 and 26. The wire 18extends at both ends thereof through the apertures of the respectivepairs of ears 24 and 26. A bead 28 is fixed to each end of the wire 18below the ear 26, and two beads 30 are fixed to the wire 18, each abovea different one of the ears 24. A bead 32 is slidably and frictionallymounted on the wire 18 between each pair of the cars 24 and 26. The wire20 is slidably connected to the rear portions of the ear cups 12 and 14in the same manner as described for the wire 18. It will now beunderstood that the ear cups 12 and 14 may be slidably adjusted withrespect to the headband 16 so as to dispose them around the ears andresiliently against the head of a wearer. Since the ear cups 12 and 14and the ear pads therefor are similar, only the ear cup 12 and itsassociated ear pad 36 will be described hereinafter in greater detail.

The ear cup 12 is generally cup-shaped and large enough to fit aroundthe ear of a person. The rim of the cup 12 is formed with a relativelywide, marginal flange 34 for the purpose hereinafter appearing. A liner35 of sound absorbing material, such as isocyanate foam, may be disposedwithin the ear cup 12, as shown.

An improved ear pad 36 according to the present invention is mounted onthe flange 34 of the ear cup 12 for disposition between the flange 34and the head of a wearer. The ear pad 36 comprises a tube-like sheath 40of pliable material having the general shape of the flange 34 formingthe rim of the ear cup 12. The ear pad 36 is formed with a peripheralinwardly extending flap 38 which embraces the flange 34 for attachingthe ear pad 36 to the ear cup 12. With this arrangement, the ear pad 36may be easily removed from the ear cup 12, if necessary. The flange 34fits between the flap 38 and the ear' pad 36. The sheath 40 of the earpad 36 should be made from a material that has the property of remainingpliable over a long period of time. A polyvinylchloride plasticplasticized with a plasticizer of di Z-ethyl hexyl phthalate,hereinafter referred to as DOP, a trade name commonly used in theplastics industry for this plasticizer, has been found to besatisfactory. It will be understood, however, that other materials, andsuitable softeners therefor, may be used within the purview of thisinvention.

The sheath 40 preferably is filled while in a somewhat collapsedcondition, with a filler, such as a mixture 42, comprising a suitablecolloid suspending medium, a plasticizer for the sheath, and asufficient quantity of very finely divided, powder in aquantitysufficient to give the mixture a paste-like consistency.

Examples of suitable mixtures for filling and sealing within a sheath ofpolyvinylchloride plastic (Formula 2951 of the Bakelite Corporation, forexample), 0.012 thick, containing about 38.26% DOP as a plasticizer, byweight, are:

Example 1 A mixture of aliphatic monoethers of polyoxyalkylene glycolsand DOP in the proportion of 66-64% and 34- 36%, by weight,respectively, when the viscosity of said glycols is 5100 Saybolt secondsat 100 F., and suificient inert powder to give, the mixture a paste-likeconsistency. The aforementioned glycols are polyoxyalkylene monohydroxycompounds. A fluid known as Ucon SO-HB- 5100, a trademark of the Carbideand Carbon Chemicals Company, comprises a mixture of gylcols suitablefor mixtures according to this example of the present invention. Adescription of these gylcols and methods of making them are described inUS. Patent 2,425,755, issued on August 19, 1947, for mixtures ofPolyoxyalkylene Monohydroxy Compoundsand Methods of Making SuchMixtures.

Example 2 A mixture of Coolanol 45 and DOP in the proportion of 4951%and 5149%, by weight, respectively, and a sufiicient quantity of inertpowder to give the mixture a paste-like consistency. Coolanol 45 is atrademark of Monsanto Chemical Company for silicate esters of theorthosilicate type having a viscosity of about 12.2 centistokes at 100F.

Example 3 A mixture of B01? and propylene glycol in the proportion of1.8-2.2% and 98.297.8%, by weight, respectively, and a sufiicientquantity of inert powder to give the mixture a paste-like consistency.

An excellent powder for the mixtures forming fillers according to thepresent invention has been found to be a finely divided powder ofcalcium silicate known as Microcell E, a trademark of the Johns ManvilleCompany. Microcell E is a synthetic calcium silicate produced by ahydrothermal reaction of diatomaceous earth with a source of calcium. Ananalysis of Microcell B shows it to be substantially:

Microcell E pours very easily because it does notordinarily cake. Inertpowders of diatomaceous earth, talc, or powdered limestone also aresuitable for mixing with suspending media such, for example, asdescribed above to obtain a mixture of paste-like consistency. For thepurpose of the present invention, paste-like mixtures having a viscositywithin the range of 500 to 10,000 centipoises may be used as the mixture42. For example, a mixture comprising 18 grams of Microcell E added to100 grams of Ucon 50-HB-5100 mixed with DOP in the proportion of 65% and35% respectively, by weight has been found suitable. The inert powdershould preferably be ground fine enough to form a colloidal solutionwith the suspending medium.

In use, the resilient headband, 16 urges the ear pad 36 against the sideof the head around the ear. Since the filler 42 of the ear pad 36 is ofa paste-like consistency over a wide range of temperatures, the pad 36quickly conforms to the contour of the wearers head. Body and hair oilsof the wearer, however, have a tendency to remove some of theplasticizer from the plastic sheath 40. Unless this plasticizer, or someother suitable softener, is replaced in the plastic sheath 40, thesheath will deteriorate. The plasticizer in the mixture 42 serves toreplace the plasticizer removed from the sheath 40 by the wearer. By theuse of proper quantities, such as in the examples given, supra, anequilibrium may be maintained between the amount of plasticizerextracted from the plastic sheath 40 by the wearer and the amount ofplasticizer donated to the plastic sheath 40 by the plasticizer from thepaste-like mixture. Under these conditions, the ear pad 36 may beconsidered to be equalized.

A mixture of paste-like consistency for the plastic sheath 40, asdescribed above, has been found to be superior to liquid fillers of theprior art from the standpoint of attenuating ambient noise, and alsofrom the standpoint of prolonging the active life of the sheathcontainer. For the purpose of the present invention, a mixture ofpaste-like consistency having a viscosity within the range of 500 to10,000 centipoises may be used in the mixture 42.

From the foregoing description, it will be apparent that there has beendescribed improved, circumaural, ear pads for a device for protectingpersonnel from noise. The mixtures of paste-like consistency describedherein will retain their pliant, flexible state over a relatively widerange of temperatures, therefore being suitable for ear pads for planeand helicopter personnel. The ear pads of the present invention may alsobe used, in a smaller size, as direct-aural noise attenuators, that is,directily in contact with the human ear. While only a few specificexamples of improved, equalized ear pads have been described, otherequalized ear pads will, no doubt readily suggest themselves to thoseskilled in the art. Hence, it is desired that the foregoing shall beconsidered merely as illustrative and not in a limiting sense.

What is claimed is:

l. A pad comprising a sheath of plasticized plastic having a fillertherein, said filler comprising a liquid, a powder substantiallyinsoluble in said liquid and a plasticizer for said plastic sheath.

2. A pad comprising an endless, tube-like sheath of a plasticplasticized with di 2-ethyl hexyl phthalate, said sheath being filledwith a mixture comprising a colloid suspending medium, an inert powdersuspended in said medium, and di Z-ethyl hexyl phthalate.

3. A pad as defined in claim 2 wherein said medium comprises mixtures ofpolyoxyalkylene monohydroxy compounds.

4. A pad as defined in claim 2 wherein said medium comprises aliphaticmonoethers of polyoxyalkylene glycols having a viscosity ofsubstantially 5100 Saybolt seconds at F.

5. In an ear protective device of the type comprising a cup adapted tofit over an ear of a person and said cup being formed with a relativelywide pad receiving surface, an ear pad mounted on said surface andcomprising an endless, tube-like sheath of a plasticized plastic havingthe general shape of said surface, said sheath being partially collapsedand filled with a mixture comprising a liquid, a powder and aplasticizer for said plastic sheath.

6. An ear pad as defined in claim 5 wherein said plasticizer is diZ-ethyl hexyl phthalate and said mixture comprises silicate estershaving a viscosity of about 12.2 centistokes at 100 F., and wherein theproportions of said di 2-ethyl hexyl phthalate and said esters are49-51% to 51-49%, by weight, respectively.

7. An ear pad as defined in claim 5 wherein said plasticizer is di2-ethyl hexyl phthalate and said liquid is propylene glycol, and whereinthe proportions of said di 2-ethyl hexyl phthalate and said propyleneglycol are 1.8-2.2% to 98.2-97.8%, by weight, respectively.

8. In an ear protective device of the type comprising a cup adapted tofit around an ear of a person, and said cup being formed with arelatively wide pad receiving surface, an ear pad mounted on saidsurface and comprising an endless, tube-like sheath of plasticizedpolyvinylchloride plastic and having the general shape of said surface,and said sheath being partially collapsed and filled with a mixturecomprising aliphatic monoethers of polyoxyalkylene glycols, an inertpowder, and a plasticizer for said plastic.

9. An ear pad as defined in claim 8 wherein said plasticizer is di2-ethy1 hexyl phthalate, and wherein the proportions of said aliphaticmonoethers of polyoxyalkylene References Cited in the file of thispatent UNITED STATES PATENTS 2,425,755 Roberts et a1. Apr. 19, 19472,666,208 Funk July 25, 1950 2,786,776 Allen Mar. 26, 1957 2,801,423Shaw et a1. Aug. 6, 1957

